Embodiments herein generally relate to devices that utilize rollers to apply material (such as printing devices) and more particularly to a device that determines the material density between rollers based upon the current flow between the rollers.
Modern printing devices utilize development systems to create markings on different forms of media. However, development systems are sensitive to changes in the amount of marking material passing through various locations, such as the donor loading nips. If there is not enough marking material, one of the first image quality defects seen is a reload defect, which appears as a ghost of a previously developed image. To the contrary, if the amount marking material is too much, the system will experience motor faults or material loss from the housing due to a flow failure.
To prevent these conditions, great effort is spent to achieve the required gaps and material flow. However, the amount of marking material can sometimes be unstable because the material flow varies with changes in toner concentration, toner age, and developer age. The result of this is that gaps and flows need to be selected to prevent failures at the most demanding conditions. Unfortunately, this will deliver poor performance at other noise conditions, particularly very low toner concentrations and low toner ages.
In order to address such situations, with embodiments herein the reload performance can be predicted using a measurement of the current flow through the magnetic roll to donor roll loading nip. Specifically, in one embodiment, a non-printing current measurement is performed during machine cycle-up and cycle-out. The result of the current measurement is then used to change the speed of the material delivery magnetic roll. If the current is below a predetermined amount, the delivery speed is increased slightly, thus increasing the developer density in the loading nips. If the current is above the predetermined limit, the delivery magnetic roll is slowed down. The current measurement performed by embodiments herein is also used in housing build and manufacture to quickly identify incorrect settings and conditions before the housing is installed in a machine.
One exemplary embodiment herein is any form of apparatus that uses a container storing a material and at least one roller (e.g., a “first” roller) that is in the container, a second roller that is adjacent the container, and that receives the material from the first roller. Further, the apparatus includes at least one additional third roller adjacent the second roller. The second roller transfers the material from the first roller to the third roller and the second roller and the third roller form a loading nip at a location where the second roller is closest to the third roller.
With this apparatus, at least one recipient device is adjacent the third roller. The recipient device receives the material from the third roller. A measurement device is also operatively connected to (e.g., electrically connected to) the second roller and the third roller. The measurement device measures current flow between the second roller and the third roller. The current flow between the second roller and the third roller occurs at the loading nip and provides an indication of a measured density of the material at the loading nip.
Further, a controller is operatively connected to the measurement device, the first roller, the second roller, and the third roller. The controller alters the relative rotation rate difference between the first roller and the second roller based on the current flow to maintain a predetermined density of the material at the loading nip. The controller alters the relative rotation rate difference between the first roller and the second roller by changing a rotational speed of the first roller relative to the second roller.
A more specific embodiment herein comprises a developer apparatus that has a container connected to a housing. The container stores a marking material. At least one supply roller is in the container, and at least one magnetic roller is within the housing. The magnetic roller receives the marking material from the supply roller. At least one donor roller is also within the housing adjacent the magnetic roller. The magnetic roller transfers the marking material from the magnetic roller to the donor roller. The magnetic roller and the donor roller form a loading nip at a location where the magnetic roller is closest to the donor roller. The donor roller transfers the marking material to at least one photoconductor adjacent the housing.
A measurement device is operatively connected to the magnetic roller and the donor roller. Again, the measurement device measures current flow between the magnetic roller and the donor roller. Further, a controller is operatively connected to the measurement device, the supply roller, the magnetic roller, and the donor roller. The controller alters the relative rotation rate difference between the supply roller and the magnetic roller based on the current flow to maintain a predetermined density of the marking material at the loading nip.
Another exemplary embodiment is a printing apparatus that comprises a container storing a marking material and at least one rotating brush contacting the marking material. At least one magnetic roller is adjacent the container. The rotating brush or magnetic supply roller transfers the marking material to the magnetic roller. Further, at least one donor roller is adjacent the magnetic roller. The magnetic roller transfers the marking material from the magnetic roller to the donor roller and the magnetic roller and the donor roller form a loading nip at a location where the magnetic roller is closest to the donor roller.
At least one photoconductor is adjacent the donor roller, and the photoconductor receives the marking material from the donor roller. Additionally, at least one charging device is adjacent the photoconductor. The charging device creates a latent electronic image on the photoconductor. The marking material adheres to the photoconductor at locations of the latent electronic image. A media supply path is positioned to supply sheets of media to the photoconductor. The photoconductor transfers the marking material, as patterned by the latent electronic image, to the sheets of media.
A current measurement device is operatively connected to the magnetic roller and the donor roller. The current measurement device measures current flow between the magnetic roller and the donor roller. A controller is operatively connected to the measurement device, the magnetic roller, and the donor roller. The controller alters the relative rotation rate difference between the supply roller and the magnetic roller based on the current flow to maintain a predetermined density of the marking material at the loading nip.
Stated as a method, one embodiment herein transfers a material from a supply roller to at least one second roller, and transfers the material from the second roller to at least one third roller. The second roller and the third roller form a loading nip at a location where the second roller is closest to the third roller. The method transfers the material from the third roller to at least one recipient device, and measures current flow between the second roller and the third roller using a measurement device. Then, the method alters the relative rotation rate difference between the supply roller and the second roller based on the current flow to maintain a predetermined density of the material at the loading nip using a controller.
These and other features are described in, or are apparent from, the following detailed description.